RESUMO

BACKGROUND: The basis of fluoroquinolone treatment failure for Mycoplasma genitalium is poorly understood. METHODS: To identify mutations associated with failure we sequenced key regions of the M. genitalium parC and gyrA genes for patients undergoing sequential therapy with doxycycline-moxifloxacin (201 patients, including 21 with failure) or doxycycline-sitafloxacin (126 patients, including 13 with failure). RESULTS: The parC G248T/S83I mutation was more common among patients with failed sequential doxycycline-moxifloxacin (present in 76.2% of failures vs 7.8% cures, P < .001) or doxycycline-sitafloxacin (50% vs 16.8%, respectively; P = .01) treatment. Doxycycline-sitafloxacin was more efficacious than doxycycline-moxifloxacin against infections carrying the parC mutation conferring S83I amino acid change. Treatment was more likely to fail in these infections if they had a concurrent gyrA mutation (M95I or D99N) (P = .07 for doxycycline-moxifloxacin group and P = .009 for doxycycline-sitafloxacin group), suggesting an additive effect. CONCLUSIONS: This study indicates that parC G248T/S83I mutations contribute to failure of moxifloxacin and sitafloxacin, and the findings will inform the development of quinolone resistance assays needed to ensure optimal selection of antimicrobials for M. genitalium.

RESUMO

Mycoplasma genitalium is a cause of non-gonoccocal urethritis (NGU) in men and cervicitis and pelvic inflammatory disease in women. Recent international data also indicated that the first line treatment, 1 gram stat azithromycin therapy, for M. genitalium is becoming less effective, with the corresponding emergence of macrolide resistant strains. Increasing failure rates of azithromycin for M. genitalium has significant implications for the presumptive treatment of NGU and international clinical treatment guidelines. Assays able to predict macrolide resistance along with detection of M. genitalium will be useful to enable appropriate selection of antimicrobials to which the organism is susceptible and facilitate high levels of rapid cure. One such assay recently developed is the MG 23S assay, which employs novel PlexZyme™ and PlexPrime™ technology. It is a multiplex assay for detection of M. genitalium and 5 mutations associated with macrolide resistance. The assay was evaluated in 400 samples from 254 (186 males and 68 females) consecutively infected participants, undergoing tests of cure. Using the MG 23S assay, 83% (331/440) of samples were positive, with 56% of positives carrying a macrolide resistance mutation. Comparison of the MG 23S assay to a reference qPCR method for M. genitalium detection and high resolution melt analysis (HRMA) and sequencing for detection of macrolide resistance mutations, resulted in a sensitivity and specificity for M. genitalium detection and for macrolide resistance of 99.1/98.5% and 97.4/100%, respectively. The MG 23S assay provides a considerable advantage in clinical settings through combined diagnosis and detection of macrolide resistance.

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